earth 1: Geological time of the earth (v1.1)
Acknowledgement to CNN for this.
Geology sounds like a dry technical subject, right? This article makes it interesting
by tying it to North America, today and you!!
How does geology mark time?
The geologic time scale provides the official framework for
our understanding of Earth’s 4.5-billion-year history. Geologists break
down our planet’s history into eons, eras, periods, epochs, and ages — with an
eon being the largest chunk of time and an age the shortest. Some
well-known past names are the Cambrian, Permian, Jurassic, and Triassic
periods.
For example, we currently live in the Meghalayan Age (which
began 2251 BCE). It’s part of the Holocene Epoch, which began at the end of the
last ice age 11,700 years ago, when ice caps and glaciers began retreating. The
Holocene is part of the Quaternary Period (which began 2.6 million years ago),
which is the most recent division of the Cenozoic Era (which began 66 million
years ago), which in turn is part of Phanerozoic Eon — which spans from 539
million years ago to the present.
Associated with each span is an abundance of information on the biota, environments, tectonics, paleogeography and more. It’s a bit like saying the Middle Ages, or the Renaissance. Every segment in the official timeline is also represented by a single geological site — known as the Global Boundary Stratotype Section and Point (GSSP) — those best captures what’s novel or unique about a particular chapter in Earth’s history. Each point is typically marked with a “golden spike,” that could provide a primary marker for the new geological epoch, often hammered in a pivotal layer of rock — although the site could be a stalagmite or core of ice.
Scientists have collected evidence
that a new era has begun, that reflects the impact of humans. There is a proposal to either name it a new epoch
(proposed name is Anthropocene and proposed start date as 1950) or a new
age. For the Anthropocene, the proposed golden spike location is sediment cored
from the bed of Crawford Lake in Ontario, Canada that reveals the geochemical
traces of nuclear bomb tests specifically plutonium, large scale burning of fossil fuels and dumping of plastics and fertilizers on land and water bodies. The lake isn’t
large, covering 2.4 hectares (5.9 acres), but it is exceptionally deep, nearly
24 meters (78.7 feet), and the sediment found at the bottom can be divided into
annual layers to be sampled for geochemical markers of human activity. The
shape (of the lake) restricts the mixing of the water column so the bottom
waters do not mix with the surface waters. The bottom of the lake is completely
isolated from the rest of the planet except for what gently sinks to the
bottom.
Geologists will present a proposal to make the Anthropocene
official to the Sub commission on Quaternary Stratigraphy later this
summer. If the Sub commission’s members agree with a 60% majority, the
proposal will then be passed on to the International Commission on
Stratigraphy, which will also have to vote and agree with a 60% majority for
the proposal to move onward for ratification. Both bodies are part of the
International Union of Geological Sciences, which represents more than 1
million geoscientists around the world. A final decision is expected at
the 37th International Geological Congress in Busan, South Korea, in August
2024. Naming a new geological epoch is a very conservative process, so there is
no guarantee that the proposal will be successful.
Some geologists feel it’s more accurate to describe
humanity’s profound impact on Earth as an ongoing geological event rather than
a formal epoch with a precise global start date. It’s also possible, they say,
that stratigraphers may decide that the Anthropocene doesn’t rise to the level
of epoch, but it could be the fourth age of the Holocene — the much less catchy
Crawfordian Age.
Above is view of Crawford lake in Ontario, Canada.
In March 2024, the geology committee officially voted against progressing the Anthropocene epoch proposal.
The rejection was not because scientists disagree about human impact. Everyone agrees that humans are profoundly changing the planet. Instead, the decision came down to how geology strictly defines time:
Too Rigid of a Start Date: The proposal restricted the start of the Anthropocene to exactly 1950. Many geologists argued that human impact is far too complex to be pinned down to a single year.
Varying Timelines: Human impact didn't happen all at once globally. It started at different times in different places—ranging from the dawn of agriculture thousands of years ago to the Industrial Revolution in the 1700s, and finally the nuclear age of the 1950s.
An Event, Not an Epoch: Geologists concluded that humanity's profound influence is better described as an ongoing "geological event" rather than a rigid, newly defined epoch.
Because the proposal was voted down, we officially remain in the Holocene Epoch.
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